To input data in a portable communication apparatus, for example a mobile phone, there are besides pushing keys on the apparatus many different types of man-machine interface solutions.
One example is a space-saving optical mouse for a mobile phone developed by Dutch researchers at the Philips Center for Industrial Technology and described on the Internet page [http://optics.org/articles/news/8/6/23/1]. The optical mouse is made up of laser diodes and a detector placed beneath a lens. The light from the laser is focused on an object, such as a fingertip, and is reflected back and thereby mixes within the internal laser cavity. A disadvantage with this technique is that it is implemented using expensive, dedicated laser technology.
The use of fingerprint is well known for controlling access to different types of systems. In WO 01/11577 A1 a system for checking the right to access sensitive information using biometric data is described.
When sharing a mobile phone between users today the users also have to share the memory content of these mobile phones, that is phonebook and calendar and the only possibility for secrecy and privacy is exchanging SIM cards when switching user. This way the different users at least get their own phonebook and inbox for SMS-messages.